# 25.000+ rows - SELECT consecutive numbers performance issue

**URL:** <https://forums.percona.com/t/25-000-rows-select-consecutive-numbers-performance-issue/3942>\
**Category:** Other MySQL® Questions\
**Created:** [December 12, 2014, 8:48am UTC](https://forums.percona.com/t/25-000-rows-select-consecutive-numbers-performance-issue/3942 "2014-12-12T08:48:07Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![daniel.negoita](https://avatars.discourse-cdn.com/v4/letter/d/c37758/32.png) [@daniel.negoita](https://forums.percona.com/u/daniel.negoita)\
**Post date:** [December 12, 2014, 8:48am UTC](https://forums.percona.com/t/25-000-rows-select-consecutive-numbers-performance-issue/3942/1 "2014-12-12T08:48:07Z")

</div>

I have tried to be as explicit as I could. Below you have the query explained in details

What I want to obtain? - I want to SELECT start\_number and end\_number from a set of consecutive numbers from a table

```auto
ex: 

I have a column with values: 1,2,3,5,7,8,9,10
If I run the SELECT on column will return: (1,3), (5), (7), (8,10)

So my result will look something like :

[
'start_number' => 1,
'end_number' => 3
]
.............
.........

```

The problem is that the table contains a large number of rows (25.000+…for now) and it takes ages to execute (I have limited the number of results returned but still didn’t fixed the execution time)

```auto
SELECT 
l.control_series AS start_control_series,
(SELECT 
MIN(a.control_series) AS id
FROM
cards AS a
LEFT OUTER JOIN
cards AS b ON a.control_series = b.control_series - 1
WHERE
b.control_series IS NULL
AND a.control_series >= l.control_series) AS end_control_series
FROM
cards AS l
LEFT OUTER JOIN
cards AS r ON r.control_series = l.control_series - 1
WHERE
r.control_series IS NULL
ORDER BY product_id ASC
LIMIT 1;

Answer returned:

[
'start_control_series' => "110",
'end_control_series' => '114',
]

MySQLWorkbench response: 1 row(s) returned 304.829 sec / 0.000 sec (as you can see it takes ages)

```

Table (cards) has 3 columns:  
[LIST]  
[_]row\_id (int primary autoincrement)  
[_]control\_series (bigint)  
[\*]product\_id (int)  
[/LIST] Running MySQL 5.1, on a shared host  
I’m want to return 10 results (LIMIT 1,10) in a fair amount of time  
Thanks in advanced, hopefully someone can help me.

![photoid=28235](https://us1.discourse-cdn.com/flex019/uploads/percona1/original/2X/d/d739dcd714a21647a91d9c7d10a113321ceb1d5a.jpeg)